A device of this general type is known from DE 199 63 094 A1. This device is configured as a so-called vane-type adjuster and essentially comprises a stator, which is in drive connection with a crankshaft of the internal combustion engine and is connected in a rotationally secure manner to a drive wheel, and a rotor, which is connected in a rotationally secure manner to a camshaft of the internal combustion engine. The stator here has a cavity, which is formed by a hollow-cylindrical peripheral wall and two side walls and in which hydraulic working spaces are formed by limit walls. The rotor includes a wheel hub and has, on the periphery of the wheel hub, blades which extend radially into respective working spaces of the drive wheel and divide each of the working spaces into, two mutually counteracting hydraulic pressure chambers. The pressure chambers of each working space are sealed one against the other. When they are pressurized simultaneously, or selectively, with hydraulic fluid from a hydraulic fluid circuit, generally with engine oil, it effects a swivel motion or fixes the rotor relative to the stator, and thus of the camshaft relative to the crankshaft.
Many of the newer rotation angle adjusting devices are integrated in the drive system of the camshaft, in the so-called control gear. In this case, mechanical vibrations are transmitted. During engine running, vibrations are generated in the crank gear, the control gear or the valve gear. If the drive wheel is operatively connected to the crankshaft, for example by a belt or a chain, the device, moreover, converts a translatory motion into a rotary motion. This conversion additionally generates mechanical vibrations.
Since, in rotation angle adjusting devices, power is transmitted by hydraulically clamped blades on the basis of the vane-cell principle, the hydraulic fluid circuit of the internal combustion engine is incorporated into the power transmission for the drive of the camshaft. Owing to air entrapment in the hydraulic fluid and internal and external oil leakage, only a limited torsional rigidity between the drive side and the power-take-off side on the device is possible. The aforementioned mechanical vibrations can therefore be transmitted to the hydraulic fluid circuit of the internal combustion engine. If the device is unfavorably disposed in the control gear, high pressures or pressure peaks, in excess of 200 bar, can consequently be generated.
In particular, if a plurality of rotation angle adjusting devices are mutually connected, for example, by a chain drive and are adjusted in phase opposition, the chain can sag. If the devices are then readjusted in phase opposition but in the opposite direction, this produces sudden high chain tensions, which are transmitted via the stators into the pressure chambers, to the hydraulic fluid, and there give rise to the pressure peaks. The greater the difference in the rotation angle of the devices, the higher are these peaks. Also, if the relative phase position of the camshaft is unfavorable, for example through increasing overlapping of the valve curves, this can result in sudden chain tensions. If the inlet cam, for example, is in the region of the lifting flank, and the outlet cam is in the region of the dropping flank, forces are generated in mutually opposed directions and this can then again give rise to the pressure peaks.
These pressure peaks are damaging both to the device and to the internal combustion engine. They reduce the durability of components in direct contact with the hydraulic fluid circuit. They adversely affect the working of hydraulically controlled systems in this hydraulic fluid circuit, such as a hydraulic chain tensioner.
To solve this problem, DE 198 37 693 A1 proposes to connect upstream of the hydraulic fluid ports of the pressure chambers, respective non-return valves, which shut off in the direction of the hydraulic pump. However, this only allows the elimination of pressure peaks which derive from camshaft alternating moments and are not high-frequency. Furthermore, additional assembly input is required to integrate further components into the hydraulic fluid circuit.